Both petroleum refineries and engine manufacturers are constantly faced with the challenge of continually improving their products to meet increasingly severe governmental efficiency and emission requirements, and consumers' desires for enhanced performance. For example, in producing a fuel suitable for use in an internal combustion engine, petroleum producers blend a plurality of hydrocarbon containing streams to produce a product that will meet governmental combustion emission regulations and the engine manufacturers performance fuel criteria, such as research octane number (RON). Similarly, engine manufacturers conventionally design spark ignition type internal combustion engines around the properties of the fuel. For example, engine manufacturers endeavor to inhibit to the maximum extent possible the phenomenon of auto-ignition which typically results in knocking, and can cause engine damage, when a fuel with insufficient knock-resistance is combusted in the engine.
Under typical driving situations, engines operate under a wide range of conditions depending on many factors including ambient conditions (air temperature, humidity, etc.), vehicle load, speed, gear ratio, rate of acceleration, and the like. Engine manufacturers and fuel blenders have to design products which perform well under virtually all such diverse conditions. This requires compromise, as often times fuel properties or engine parameters that are desirable under certain speed/load conditions prove detrimental to overall performance at other speed/load conditions. Conventionally, vehicular fuels are supplied in two or three grades, typically distinguished by their Research Octane Number, or RON. Generally, the selection of fuel grade is based upon the engine specifications. However, once the fuel is “onboard,” it becomes a “one fuel fits all” and must be designed to accommodate diverse speed, load and other driving conditions.
Attempts have been made to overcome the limitations of providing only a single grade of fuel for driving an internal combustion engine. In such attempts, systems have been developed for providing multiple fuels of different RON numbers “onboard” a vehicle, for driving the associated internal combustion engine with individual ones or mixtures of the fuels in a controlled manner for meeting the engine's drive cycle conditions over a broad range of operating conditions of the engine. Although these prior systems do offer an enhanced performance of an internal combustion engine, it is clear to those of skill in the art that such systems require further improvement.